Nuclear apparatus



G. E. MALLINCKRODT 3,107,210

Oct. 15, 1963 NUCLEAR APPARATUS Filed June 26, 1959 2 W 3 ll w 1 a 7/ Z72% 27 L Q L c Q 6??? Z??? k c Z 3 R 2 w flliw 3,107,210 NUCLEARAPPARATUS George E. Mallinckrodt, 20 Kingsbury Place, St. Louis 12, M0.Filed June 26, 1959, Ser. No. 823,250 1 Claim. (Cl. 204-1032) Thisinvention relates to nuclear apparatus, and more particularly toapparatus for inducing nuclear reactions.

Among the several objects of the invention may be noted the provision ofapparatus for inducing nuclear reactions, and the provision of suchapparatus which is comparatively safe in operation and economical inconstruction. Other objects and features will be in part apparent and inpart pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofwhich will be indicated in the following claim.

In the accompanying drawings, in which one of various possibleembodiments of the invention is illustrated,

FIG. 1 is a schematic layout of one form of the invention;

FIG. 2 is a greatly enlarged fragmentary section of a fuel element,being taken on line -22 of FIG. 1;

FIG. 3 is a cross section of said fuel element taken on line 3-3 of FIG.2;

FIG. 4 is a view similar to FIG. 1, showing an application of theinvention; and

=F-IG. 5 is an enlarged cross section taken on line 5-5 of =F-IG. 1.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

Referring now more particularly to FIG. 1, numerals 1 and *3 indicatespaced insulating supports for a pair of one-half inch or so diametercylindrical electrodes 5 and 7, respectively. Quartz is a suitablematerial for such insulating supports. Electrode 7 is faced with a discof tungsten or tungsten carbide, as shown at 9. The parts 5 and 7 arecomposed of highly conductive material such as copper, silver or thelike, adapted to present a very low resistance to a large flow ofcurrent. For example, the cross sections presented to current flowthrough electrodes 5 and (7, 9) may be on the order of three quarters ofa square inch or more in area.

At numeral '11 is shown a condenser of, for example, a capacity fromabout one to ten farads inclusive, although this is not to be taken aslimiting. One side of the condenser is connected with electrode 5 bymeans of a lead 13. A switch 14 may be located in this lead. The otherside of the condenser '11 is connected to electrode (7, 9) by means of alead =15. Although both leads 1 3 and =15 are shown diagrammatically bymeans of lines, it is to be understood these leads v13 and 15 are alsocomposed of highly conductive material such as copper or silver and alsohave substantial cross sections on the order above given. The purpose ofhaving the conductive elements 5, 7, 9, 13 and '15 of large crosssections is to present small resistance to flow of current so as toreduce the time constant of the circuit of which they form a part whenthe condenser 11 is discharged in the manner set forth below. Thecondenser 11 is adapted to be charged from a suitable high-voltage D.C.generator 17. A suitable voltage is 1,000 to 10,000 volts or so but thisis not to be taken as limiting.

The electrode 5 is provided with a central small axial bore 19 which,for example, may be on the order of .060 inch in diameter for thesliding acceptance with minimum clearance of the needle-like end 21 of acylindrical capil- 3,107,2l Patented Oct. 15, 1963 ice lary tube orshell 23. The shell may be of any suitable length but for continuousoperation it is made of substantial length and wound upon a reel or drum25. Details of this tubing are shown in FIGS. 2 and 3. Its outside wallis preferably composed of silver or copper, but this may be composed ofmaterial of low atomic number, such as beryllium. An important propertyof the jacket is high conductivity.

The tubing 23 is filled with a core composed of needles of nuclear fuelmaterial 31 separated at intervals by short lengths of a quenchingmaterial 32 of high atomic number such as tungsten. The lengths areanchored by crimps 27, to form cylindrical encapsulations 29 in whichare located what may be referred to as spaced sections 31 of fuel..These needle sections 31 may be approximately inch in length. Thelengths 32 may be /a inch long. This produces a inch pitch distance D. Asuitable core material for the needle sections is a lithium hydrideconsisting of lithium deuteride with 1% to 10% inclusive by weight oflithium triteride. This form of core material is solid.

The outside diameter of the tubing 23 may be .060 inch and its insidediameter .010 inch, which corresponds to .025 inch as its wallthickness. This corresponds also to a diameter of each needle portion 31 of .010 inch. It is to be understood that the Wall thickness of thecapillary tubing 23 may range from said .025 inch down to .010 inch, inwhich event its outside diameter will range from said .060 inch to .030inch. It will therefore be understood that the range of the diameter ofthe passage 19 in the electrode '5 is also from .060 inch down to .030inch, in order to accept the wire with a close sliding fit.

-It is important that the outside walls of the needle portions 3 1 andthe inside and outside walls of the tubing 23 shall be highly concentricaround a center line CL and that their various diameters shall beconstant throughout the axial lengths of the needle portions 31 withinthe capsule-forming tube walls between the tcrimps or pinches 27. Thusthe tolerances of the wall thickness of the tubing 23 between pinches 27should be on the order of .0001 inch and the walls of the tubing and ofthe needles should be concentric within .00005 inch. It is alsodesirable that line CL shall be central in the cylindric forms of theelectrodes 5 and (7, 9). This favors the desired condition that currentflow through any portion of the tubing placed in circuit between theelectrodes 5 and (7, 9) will be of even density throughout the crosssection of such portion. Thus it 'will be seen that cylindr-ic symmetrythroughout most of the needle portions 31 between pinches 27 isimportant. Symmetry is not important at the pinches. In fact, someasymmetry at the pinches is of some advantage.

The lower end of the electrode 5 is countcrbored, as shown at 33, andthreaded for the acceptance of an axially slitted outlet springy collet35 having a hole through it for Iclosely slidably fitting the capillarywire 23. A threaded thimble 30 holds the collet in place. The threeconventional collet slits, being out of the paper plane, do not appearin FIG. 1, but are shown at 36 in FIG. 5. Behind the collet 35 in thecounterbore 33 is a suitable fibrous packing of a highly conductivematerial 34, such as compacted threads of silver adapted to form aconductive brush between the electrode 5' and the contained capillarywire 23.

The reel 25 is supported above a suitable feeder mechanism 37, mountedon insulation 39 above the electrode 5. The capillary tube 23 is drawnfor example by resilient grip rolls 38 of the feeder from the reel 25and fed through the electrode 5 toward the electrode facing 9. Duringfeed, the collet slits open slightly; otherwise they close. The feed ispreferably of the intermittent va- I for circulation.

riety and may be manually controlled or, if desired, automaticallycontrolled. Under some circumstances a continuous feed is desirable.Details of the feeder are not elaborated because various appropriatetypes are known in the art.

At the start of operation, the middle of a pinch 27 of the capillarytubing or 'shell 23 will be located at the outlet end 40' of the collet35. The spacing of the tungsten electrode facing '9 from this end 40 ofthe tubing will be on the order of the pitch distance D between thecenters of the pinches 27. .Thus an advance of the end 40 of the tubing23 toward the tungsten electrode 9 of one pitch distance will bring oneof the needle sections 31 into the gap between the electrodes ultimatelycontacting facing 9.

Assuming that the generator 17 has charged'the condenser 11, contactwill occur between the advancing pinch 27 of tubing 23 and the tungstenelectrode 9, as shown by the dotted lines at the end of 23', which willthen suddenly discharge the condenser 11 through the conductive shell 23extending in contact between the electrodes. This discharge occursrapidly in View of the low time constant of the condenser circuit andwith a flow of very heavy current through the shell andits contents 31and 32 in the gap between electrodes. This instantly saturates andvaporizes the exposedshell between the electrodes around a needle 31.Since the initial current flow between the electrodes is in the form ofa cylinder which is accurately symmetrical about axis CL, the generationof the vapor will also occur initially in a symmetrical form around thecontained needle of lithium hydride. The instantaneous result will betwo-foldz (a) An imploding cylindrical shock wave will convenge at onceupon the center line CL of the contained lithium hydride needle. Such ashock wave is pure theory, assuming errorless cylindric symmetry aboutCL, should produce an infinite temperature at this center line. Inpractice, the temperature is of course finite but extremely high, itsdegree dependingupon the accuracy with which the imploding cylindricalshock wave at a given time converges all along the center line. With thesymmetry brought about by tolerances on the order of those abovedescribed, the temperature rise in the present case is suificient,coupled with the high density afforded by the contained solid lithiumhydride needle, to induce a nuclear reaction therein. The exacttemperature that will be obtained is ditlicult to estimate or measure,but it is suificient to bring about the desired nuclear reaction.

(b) A magnetic pinch effect occurs, aiding the implosion and thus thetemperature increase,

After the needle section disappears by vaporization and entry into thereaction, more of the tubing is or may be advanced from the reel .25 forsubsequent cycles of operation.

The exposed extending portion (but not all) of the tungsten quenchsection 32 at the collet 35 will also disappear. Such a section 32 notonly forms a mechanical block to progress of the reaction to the nextneedle or fuel element 311, but in partially vaporizing releases largequantities of Brehmsstrahlen rays having a localized quenching efiect onthe reaction,

In FIG. 4 is illustrated one application of the present invention.Referring now to FIG. 4, a pressure container 41 is arranged between theinsulators 1 and 3 and surrounding the electrodes and (7, 9). Anatmosphere of helium may be maintained in the container 41 by use of apump 43 which pumps helium from a helium sump 45 into the container, areturn line 47 being Inlet and outlet check valves 49 and 51,

employed comes pressurized by heating and may be employed as anoperating medium for a prime mover such as shown at 53, which is fedfrom the container 41 over a line 55 V in which is a suitable controlvalve 57. If desired, several units such as shown in FIG. 4 may supplyone prime mover, the nuclear reactions within the respective units beingtimed for sequential operations so as to minimize the effects ofpulsations upon the prime mover.

' Broadly considered, the invention consists in subjecting a smallaccurately cylindrical needle of lithium hydride to a cylindricallyimploding shock wave established by application of current to acylindrical conductive jacket which is accurately concentric around theneedle, the application of the current being large and sudden enough tovaporize the needle at once, whereby a shrinking accurate cylindn'cgeometry of the shock wave is established and maintained as it implodesthrough the needle of fuel 31 and on the center line CL.

Although the core of fuel material 31 is herein shown as being solid, itwill be understood that it may be of liquid form, provided the pinches27 are caused to close off the tubing 23 at the appropriate intervals,entrapping such liquid material in elongate cylindrical segments.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

I claim: 7 a Nuclear apparatus comprising a pair of spaced electrodes,one of said electrodes having an opening therethrough to receive a fuelassembly which includes cylindrical needle-like cores of solid Jithiumhydnide separated by short lengths of tungsten and enclose-d by acylindrical jacket composed of conductive material and being of cap- 1illary dimensions, a condenser of substantial capacity, a

high-voltage generator, means for connecting said generator across saidcondenser to change said condenser to a high voltage, means forconnecting said charged condenser across said electrodes, and means forpositioning a portion of said fuel assembly including one of saidlithium hydride cores between said electrodes to provide a current paththerebetween, whereby said condenser is discharged through said portionof said fuel assembly, the current therethrough being sufiicient tovaporize the conductive jacket thereof and thereby implode a cylindricalshoolc wave concentrically upon the contained lithium hydride coreso'that the temperature of said core is raised sufficiently to inducenuclear reactions therein.

References Cited in the file of this patent FOREIGN PATENTS 508,233Great Britain June 28, 1939 774,052. Great Britain May 1, 1957 1,0 22,71l Germany Jan. 11, 1958 OTHER REFERENCES Progress, October 1955, pp. 482

